Diseases of the cardiovascular system affect millions of people each year and are a leading cause of death throughout the world. The costs to society from such diseases is enormous both in terms of the lives lost and in terms of the cost of treating patients through traditional surgical techniques. A particularly prevalent form of cardiovascular disease is a reduction in the blood supply leading to the heart caused by atherosclerosis or other condition that creates a restriction in blood flow at a critical point in the cardiovascular system that supplies blood to the heart. In many cases, such a blockage or restriction in the blood flow leading to the heart is treated by a surgical procedure known as a Coronary Artery Bypass Graft (CABG) procedure, more commonly known as a “heart bypass” operation. In the CABG procedure, the surgeon “bypasses” the obstruction to restore normal blood flow to the heart by attaching an available source vessel to an obstructed target coronary artery or by removing a portion of a vein or artery from another part of the body, to use as a graft, and by installing the graft at points between a source vessel and a target artery to restore normal blood flow.
Although the CABG procedure has become relatively common, the procedure itself is lengthy and traumatic and can damage the heart, the cardiovascular system, the central nervous system, and the blood supply itself. In a conventional CABG procedure, the surgeon must make a long incision down the center of the chest, cut through the entire length of the sternum, perform several other procedures necessary to attach the patient to a heart-lung bypass machine, cut off the blood flow to the heart, and then stop the heart from beating in order to complete the bypass. The most lengthy and traumatic surgical procedures are necessary, in part, to connect the patient to a cardiopulmonary bypass (CPB) machine to continue the circulation of oxygenated blood to the rest of the body while the bypass is completed.
Although several efforts have been made to make the CABG procedure less invasive and less traumatic, most techniques still require cardiopulmonary bypass (CPB) and cardioplegia (stopping the heart). The safety and efficacy of the CABG procedure could be improved if the surgeon could avoid the need to stop the heart from beating during the procedure, thereby eliminating cardiopulmonary bypass and the lengthy and traumatic surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine to sustain the patient's life during the procedure. In recent years, a small number of surgeons have begun performing CABG procedures using surgical techniques especially developed so that the CABG procedure could be performed while the heart is still beating. In such procedures, there is no need for any form of cardiopulmonary bypass, no need to perform the extensive surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine, and no need to stop the heart. As a result, the surgery is much less invasive and the entire procedure can typically be achieved through a small number, typically one or two, comparatively small incisions in the chest.
Despite the advantages, the beating-heart CABG procedure is not widely practiced, in part, because of the difficulty in performing the necessary surgical procedures using conventional surgical instruments. If specially designed instruments were available so that the CABG procedure could be performed on the beating heart, the beating-heart CABG procedure would be more widely practiced and the treatment of cardiovascular disease in a significant patient population would be improved.
As noted above, the CABG procedure requires a fluid connection for restoring the flow of blood be established between two points to “bypass” a diseased or obstructed area to restore blood flow to the heart. This procedure is known as an “anastomosis.” Typically, a source vessel, such as a source artery with an unobstructed blood flow, i.e., the left internal mammary artery (LIMA), or a bypass-graft having one end sewn to an unobstructed blood source such as the aorta, is sewn to a target occluded coronary artery, such as the left anterior descending (LAD) artery or other vessel, that provides blood flow to the muscles of the heart. Because the beating-heart CABG procedure is performed while the heart muscle is continuing to contract and pump blood, the anastomosis procedure is difficult to perform because the heart continues to move while the surgeon is sewing the anastomosis.
The specific part of the surgical procedure that creates the anastomosis in the beating-heart CABG procedure requires placing a series of sutures through extremely small vessels on the surface of the heart and requires completing the anastomosis while the heart muscle continues to beat to pump blood during the procedure. Moreover, the sutures must be carefully placed so that the source vessel or graft is firmly attached when the anastomosis is complete and does not leak when blood flow through the vessel is established. It is also important that the anastomosis procedure be performed rapidly because the blood flow through the target coronary artery may be temporarily interrupted or reduced to avoid excessive blood loss. Also, the working space and visual access are limited because the surgeon may be working through a small incision in the chest or may be viewing the procedure on a video monitor if the site of the surgery is viewed via a surgical scope.
In one current practice, the surgeon places sutures through the heart tissue and, by exerting opposing tension on the sutures, stretches the tissue surrounding the site of the anastomosis to partially reduce the motion of the heart while the anastomosis is completed. This approach is far from ideal. Alternatively, a suction device may be attached to the surface of the heart to fix the motion of the outer layer of surface tissue. In such cases, a suction device typically has several ports incorporated into an instrument that may be attached to the heart to apply a negative pressure to the surface tissue. The negative pressure essentially attaches the surface tissue to the apparatus thereby fixing the position of a portion of the surface of the heart. Such devices are described in U.S. Pat. No. 5,727,569.
While the negative pressure approach may be effective in fixing a portion of the surface tissue of the heart, the negative pressure applied to cardiac tissue can result in temporary hematomas at the site where the suction ports attach to the tissue. Also, the exterior cardiac tissue is fixed in a configuration defined by the shape of the instrument and the orientation of the suction ports. While the heart continues to beat, the heart muscles are contracting to pump blood, which results in the muscles exerting a force directed away from the exterior tissue fixed by suction.
The beating-heart CABG procedure could be greatly improved if the heart could be stabilized during the procedure such that the motion of the heart, particularly at the site of the anastomosis, is minimized even though the heart continues to beat to supply blood to the body. If effective means for stabilizing the beating heart were available, the beating-heart CABG procedure could be performed more easily, more rapidly, more safely, and with less trauma to the patient.